Annual or lives for more than one year but less that two, erect herb or shrub (0.5–2.5 m tall); stems reddish-purple, smooth, hairless or sparsely hairy, four-angled or grooved when young becoming greenish-brown and rounded.

Leaves: Green, once-divided (15–20 cm long), with 3–5 pairs of oppositely held egg-shaped or oval leaflets (3–10 cm long and 2–3 cm wide) with broad and rounded bases, tapering towards the end with pointed tips; conspicuous gland at the base of each leaf stalk; alternately held on stems on reddish stalks (3–5 cm long).

Dense stands can displace native plant species, and reduce livestock carrying capacities in managed and natural pastures. Being allelopathic, it inhibits the germination and growth of other plants. Studies have shown that it has a negative impact on maize (Arora, 2013) and cotton yields (Higgins et al., 1986), and is an alternative host for crop diseases (Suteri et al., 1979). The seeds of S. occidentalis are highly toxic, containing compounds that damage the liver, the vascular system and the heart and lungs of domestic livestock, often leading to death in cattle (Barros et al., 1999), horses (Riet-Correa et al., 1998), goats (Suliman et al., 1982; Suliman and Shommein, 1986), pigs (Martins et al., 1986), poultry (Haraguchi et al., 1998), and rabbits (O’Hara and Pierce, 1974). Consumption of the seeds in western Uttar Pradesh, in India, resulted in the deaths of nine children within five days (Vashishtha et al., 2007).

Source:

Witt, Arne. 2017. Guide to the Naturalized and Invasive Plants of Southeast Asia. CAB International. Retrieved from http://www.cabi.org/cabebooks/ebook/20173158961 on 24 October 2018

Thick mats reduce light penetration into water bodies, impacting negatively on submerged aquatic plants. Infestations also often out-compete rooted and submerged native plants and in so doing, reduce plant diversity (Sculthorpe, 1985). Benthic fauna is usually also reduced (Coates, 1982), while fish can also be impacted by changes in oxygen concentrations as S. molesta plants die and rot within water bodies (Sculthorpe, 1985). It is also a pest of rice paddies in India, where it competes for water, nutrients and space, resulting in poor crop production (Anonymous, 1987). Dense mats also provide habitats for many human disease vectors such as Mansonia spp. mosquitoes, which have been identified as vectors of West Nile virus, St. Louis encephalitis, Venezuelan equine encephalitis and rural elephantiasis (Pancho and Soerjani, 1978; Chow et al., 1955; Ramachandran, 1960; Lounibos et al., 1990). Mats also harbour snails that transmit schistosomiasis (Holm et al., 1977). Infestations also impact negatively on water transport and fishing. For example, entire villages, dependent on water transport were abandoned along the Sepik River in Papua New Guinea when infestations of S. molesta limited access to healthcare, education and food (Gewertz, 1983).

Source:

Witt, Arne. 2017. Guide to the Naturalized and Invasive Plants of Southeast Asia. CAB International. Retrieved from http://www.cabi.org/cabebooks/ebook/20173158961 on 24 October 2018

Pterois volitans has elongated venomous dorsal fin spines and anal fin spines. It has 13 dorsal spines, 10 to 11 dorsal soft rays, 3 anal spines, 6 to 7 anal soft rays. Coastal populations are generally darker, sometimes almost black in estuaries (FishBase 2006). The membranes of fins are often spotted. The body is white or cream coloured with red to reddish-brown vertical stripes. The vertical stripes alternate from wide to very thin and sometimes merge along the flank to form a V (Schofield and Fuller 2006). The maximum length of an adult is 38cm (FishBase 2006) and the maximum body weight is 1.1kg to 1.2kg (Fishelson 1997). Reports of a 43cm individual have been obtained in its introduced range.

Eggs and larvae of the red lionfish may be transported via ballast water (Whitfield 2002).

IMPACTS

Ecosystem change: While few ecological studies have been conducted (but see Albins & Hixon 2008) it is clear that the lionfish’s presence in the Caribbean is a worrying one. Lionfish are highly piscivorous and reduce the recruitment of juvenile fishes, which in turn disrupts marine ecosystem processes and reduces reef biodiversity (Albins and Hixon 2008; Morris et al. 2008).

Reduction in native biodiversity: If their populations are allowed to continue growing unchecked, lionfish have the potential to severely reduce reef biodiversity, with the possible extinction of several species; although it is still too early to be definitive, anecdotal evidence from the Bahamas corroborates this premise (Dell 2009).

Predation: Albins and Hixon (2008) showed that lionfish can drastically reduce recruitment of native fishes on small patch reefs in the Bahamas. They are potentially capable of decimating indigenous reef fish populations in the Caribbean due to their lack of natural predators and voracious appetite (Valdez Mascari & Aguiar 2009).

Competition: Not only do lionfish consume large quantities of juvenile fish (such as grouper and yellow-tail snapper) but they also out-compete native species (such as scamp, gag, and yellowmouth grouper) for food (Morris et al. 2008; Dell 2009). Economic/Livelihoods: In addition, by reducing populations of commercially important species such as grouper (Albins and Hixon 2008) they may as a consequence damage the economy of island communities which are dependent on such fishing industries.

Human health: Lionfish are venomous with their spines containing apocrine-type venom glands (Morris et al. 2008). Lionfish venom has been found to cause cardiovascular, neuromuscular, and cytolytic effects ranging from mild reactions such as swelling to extreme pain and paralysis in upper and lower extremities (Kizer et al. 1985, in Morris et al. 2008). The toxin in lionfish venom contains acetylcholine and a neurotoxin that affects neuromuscular transmission (Cohen and Olek 1989, in Morris et al. 2008). Lionfish spines can prove dangerous to divers, snorkelers and aquarium enthusiasts (Morris et al. 2008; Schofield 2009). Stings are not fatal, but intensely painful and often requiring hospitalisation (Morris et al. 2008). Lionfish stings can be treated by heating the afflicted part in hot water (to 45° C) for 30 to 90 minutes and applying corticoids to the area (FishBase 2006); medical attention should be sought immediately (Cayman Islands Government Undated).

Displaces native plant species and reduces the abundance and diversity of bird and other animal species. In Ethiopia, P. juliflora has reduced understorey basal cover for perennial grasses and reduced the number of grass species from seven to two (Kebede and Coppock, 2015). By transforming habitats and eliminating pasture species, it threatens the survival of Grévy’s zebra (Equus grevyi) in invaded areas (Kebede and Coppock, 2015). Other negative impacts include encroachment onto paths, villages, homes, water sources, crop- and pasturelands; and injuries inflicted by the thorns (Maundu et al., 2009). Infestations have contributed to the abandonment of agricultural land, homes and small villages. The pollen has been identified as a major allergen (Killian and McMichael, 2004). In semi-arid parts of Africa, P. juliflora has depleted the natural resources on which thousands of people depend, spawning conflict between communities over the diminishing resources.

Source:

Witt, Arne. 2017. Guide to the Naturalized and Invasive Plants of Southeast Asia. CAB International. Retrieved from http://www.cabi.org/cabebooks/ebook/20173158961 on 24 October 2018